Oxy-and Amino-Benzo-1,3-Azoles

The benzo-l,3-azol-2-ones exist in the carbonyl tautomeric forms, lndazol-3-one, however, at least in dimethylsulfoxide solution, is largely in the hydroxy tautomeric form, in contrast to 1,2-benzisothiazol-3-one, which is wholly in the carbonyl form, in the solid.  

It is possible to be qnite selective in the introdnction of alkyl groups onto one of the two nitrogens of 3-hydroxyindazole. Reaction with a halide in nentral solntion, no donbt involving the imine tautomer, is selective for N-2 ° the anion reacts at N-1.  

Hot aqueous base brings abont hydrolytic cleavage of the heterocyclic ring of benzo-l,3-azol-2-ones giving the corresponding ortfto-disnbstitnted benzene. Alkylation in basic medinm generally leads to N-and 0-substitution thiones alkylate on the thione snlfnr.  

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